There are a number of circumstances in the treatment of slurries in which it is desirable to transfer praticles of the slurry from a first liquid, to a second liquid. This is particularly so in the pulp and paper art in which slurries of comminuted cellulosic fibrous material are present in a first treatment liquid, and it is desired to transfer the slurry particles to a second treatment liquid.
According to the present invention, a simple apparatus and method are provided for effecting the transfer of particles in a slurry, particularly cellulosic fibrous material particles, from one treatment liquid to another. Not only is the apparatus and method according to the invention simple and easy to construct and practice, the general concepts thereof allow great flexibility so that the concentration of particles in the slurry can be greatly changed during transfer of the particles from the first to the second liquid, allowing the slurry to be thickened or diluted.
According to the method of separating particles from the slurry of the first liquid and the particles, and feeding the particles into a second liquid flow, according to the invention, the following steps are practiced: The slurry of first liquid and particles is caused to flow in a first direction. Particles from the slurry are captured as it flows in the first direction, to separate the particles from the flow. A flow of the second liquid is established in a direction generally opposite to the first direction; and the captured particles are moved into operative association with the flow of the second liquid so that the captured particles are entrained in the second liquid. As mentioned above, the method has particular application to the handling of slurries of comminuted cellulosic fibous material (paper pulp), and in particular switching the slurry particles from one treatment liquid to another, distinct treatment liquid, although the process can also be applied to transferring the particles to a higher or lower pressure flow of the same liquid, or merely as a way of effecting thickening or dilution of the slurry. Alternatively thickening or dilution of the slurry can be accomplished at the same time as the particles are transferred from one treatment liquid to a second distinct treatment liquid.
An exemplary assembly according to the invention includes a liquid tight pressure resistant vessel defining an open interior, with partitions for dividing the open interior into first and second distinct chambers which are isolated from each other except at a slit at amid portion thereof. An inlet for the first liquid slurry and an outlet for the first liquid are operatively connected to the first chamber, while an inlet for the second liquid and outlet for the second liquid with entrained particles is operatively connected to the second chamber. A screening disk screens particles from the first liquid slurry in the first chamber and allows the particles to be entrained by the second liquid flow in the second chamber. The screening disk preferably comprises a generally circular screen sandwiched between first and second circular disk plates having through-extending openings therein, with the openings in the first plate, and the screen, defining pockets in which the particles are captured. This disk is mounted so that it fills the slit in the partition, extending generally transverse to the partition, and is rotatable about an axis generally parallel to the partition. The disk is rotated so that points spaced from the axis thereof move from one chamber to the other during rotation. Flanges associated with the partition in the vessel, and the shape of the pockets and the disk (and the solid areas between the pockets), are designed so that a pocket does not communicate with both chambers at the same time, and little liquid moves from one chamber to the other.
It is the primary object of the present invention to provide for the simple, effective, and versatile transfer of particles from a first liquid to a second liquid. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.